1. Field of the Invention
The present invention relates to a zoom lens suitable for a television camera, a motion-picture camera, a video camera, a photography camera, and a digital camera, and more particularly, to a zoom lens having a high magnification, a small size and light weight, and little aberration deviation due to focus adjustment, and to an image pickup apparatus including the zoom lens.
2. Description of the Related Art
Conventionally, as for a zoom lens in which focus adjustment is performed by a lens unit disposed closer to an object side with respect to a magnification-varying lens unit, there are proposed various types of so-called floating focus systems in which multiple lens units move for focusing.
For instance, Japanese Patent Application Laid-Open No. H07-151966 discloses a zoom lens in which a first lens unit includes a first sub-lens unit having negative refractive power, a second sub-lens unit having positive refractive power, and a third sub-lens unit having positive refractive power, and both the second sub-lens unit and the third sub-lens unit move to the object side when the focus adjustment is performed from an object at infinity to an object at a short distance.
Further, Japanese Patent Application Laid-Open No. H09-258102 discloses a zoom lens in which a first lens unit includes a first sub-lens unit having negative refractive power, a second sub-lens unit having positive refractive power, and a third sub-lens unit having positive refractive power, and the second sub-lens unit moves to an image side and the third sub-lens unit moves to the object side when the focus adjustment is performed from an object at infinity to an object at a short distance.
The zoom lens used for a television camera, a motion-picture camera, or the like is desired to achieve a higher magnification as well as a small size and light weight in order to secure mobility and to improve flexibility of photography. In addition, the zoom lens is required to have high performance with little aberration deviation due to focus adjustment. Further, a lens used for motion-picture filming or commercial filming is desired to suppress a size variation of a subject due to focus adjustment (hereinafter, referred to as breathing).
It is difficult to suppress the breathing by the focus adjustment method described in Japanese Patent Application Laid-Open No. H07-151966.
A focus adjustment method described in Japanese Patent Application Laid-Open No. H09-258102 is suitable for a wide-angle zoom lens, but it is difficult to achieve a small size and light weight as well as a high magnification.